Mass spectrometry based characterization of Hb Beckman variant in a falsely elevated HbA_1c sample

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• 作者：Rajdeep Das^a ; Monita Muralidharan^a ; Gopa Mitra^a ; Vijay Bhat^b ; Boby Mathew^a ; Debnath Pal^c ; Cecil Ross^d ; Amit Kumar Mandal^a ; ^{amit@sjri.res.in" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Cation exchange HPLC ; HbA1c ; Hb Beckman ; Hemoglobin variant ; Mass spectrometry ; Glycemic index
• 刊名：Analytical Biochemistry
• 出版年：2015
• 出版时间：15 November 2015
• 年：2015
• 卷：489
• 期：Complete
• 页码：53-58
• 全文大小：1339 K

文摘

Glycated hemoglobin (HbA_1c) is a ‘gold standard’ biomarker for assessing the glycemic index of an individual. HbA_1c is formed due to nonenzymatic glycosylation at N-terminal valine residue of the 尾-globin chain. Cation exchange based high performance liquid chromatography (CE–HPLC) is mostly used to quantify HbA_1c in blood sample. A few genetic variants of hemoglobin and post-translationally modified variants of hemoglobin interfere with CE–HPLC-based quantification, resulting in its false positive estimation. Using mass spectrometry, we analyzed a blood sample with abnormally high HbA_1c (52.1%) in the CE–HPLC method. The observed HbA_1c did not corroborate the blood glucose level of the patient. A mass spectrometry based bottom up proteomics approach, intact globin chain mass analysis, and chemical modification of the proteolytic peptides identified the presence of Hb Beckman, a genetic variant of hemoglobin, in the experimental sample. A similar surface area to charge ratio between HbA_1c and Hb Beckman might have resulted in the coelution of the variant with HbA_1c in CE–HPLC. Therefore, in the screening of diabetes mellitus through the estimation of HbA_1c, it is important to look for genetic variants of hemoglobin in samples that show abnormally high glycemic index, and HbA_1c must be estimated using an alternative method.